Plain English Meaning

A ground-based radio system that guides an aircraft down to a runway when the pilot can't see it well, by showing whether the plane is left or right of the runway centerline and whether it's too high or too low on the descent path.

Full Definition

A precision approach system that provides pilots with horizontal and vertical guidance to a specific runway. It uses radio signals — a localizer for left/right alignment with the runway centerline, and a glideslope for the correct descent angle — together with or distance-measuring equipment to indicate progress along the .